QtRoundedRectItem: when changing a pen's width, the content must stay at the same place

[richelbilderbeek]

When I change the pen's width, the content moves. Instead, the content must stay in place.

1) Write tests to break it, fix each test to correct it. In all tests, the content must stay in the same position.

• Put a reference QGraphicsRectItem and a QtRoundedRectItem in a QGraphicsView, both with 1x1 white pixels inside. Change the QGraphicsRectItem its pen width from 1 to 2.
• Put a reference QGraphicsRectItem and a QtRoundedRectItem in a QGraphicsView, both with 1x1 white pixels inside. Change the QGraphicsRectItem its pen width from 2 to 1.
• Put a reference QGraphicsRectItem and a QtRoundedRectItem in a QGraphicsView, both with 5x3 white pixels inside. The QtRoundedRectItem must have focus. Change the QtRoundedRectItem focus pen's width from 3 to 1. Lose focus. Change the QtRoundedRectItem contour/normal pen's width from 2 to 1.

2) Fix the text 3) Check visually

[richelbilderbeek]

Fixed, except for #244